The utilization of water-based metal working lubricants and coolants has become well established in light to medium-duty applications such as cutting and grinding. Such fluids not only remove heat, but also serve to inhibit corrosion, lubricate, reduce surface tension, provide extreme pressure lubrication, and control bacterial growth.
In the past, oil-based lubricant additives in most cases provided suitable anti-wear and extreme pressure performance by the use of chlorinated paraffins or waxes in their formulations. However, with increasing environmental demands, relating both to use and disposal, emphasis has been placed on the use of water-based fluids thus minimizing the presence of mineral oils and minimizing the use of chlorinated hydrocarbons.
U.S. Pat. No. 4,575,431 (Salentine, Mar. 11, 1986), relates to extreme pressure additives for lubricating oils. More particularly, the reference relates to the finding that the extreme pressure properties of a lubricant are greatly improved by the addition of a specific mixture of phosphates, said phosphates comprising: (a) substituted dithiophosphates, and (b) mono and di-substituted sulfur-free phosphates wherein the composition has been neutralized by reaction with a hydrocarbyl amine.
European Patent Application 116,399 (Forsberg, U.S. Ser. No. 456,219; filed Jan. 7, 1983), relates to phosphorus, sulfur, and nitrogen-containing salts prepared from dithiophosphorus compounds and polyamines, which salts are characterized by their anti-wear and extreme pressure properties. More particularly, the reference relates to novel phosphorus, sulfur, and nitrogen-containing salts prepared from dithiophosphorus acids selected from the group consisting of dithiophosphoric, dithiophosphinic, and dithiophosphonic acid compounds and polyamines. This reference further relates to aqueous compositions for use as functional fluids for use in hydraulic and metal cutting applications comprising a continuous aqueous phase, a dithiophosphorus acid/amine salt, and optionally a surfaceactive agent.